The design was revived in 1927 as part of Boeing's tender for newly-privatised airmail routes. Designated the Model 40A, this variant was powered by an air-cooled Pratt & Whitney Waspradial engine, which offered a 200 lb weight saving over the water-cooled Liberty specified by the postal service in 1925. Although the primary purpose of the aircraft was to carry mail, two passengers could be accommodated in the small cabin, allowing Boeing to operate it on any of the routes that the firm might bid for. The original fuselage design was changed to one using welded steel tubing.

Boeing successfully bid on the San Francisco-Chicago route, and Boeing Air Transport commenced operations on 1 July 1927 with 24 Model 40As.

Survivors

As of February 17, 2008, Boeing 40C S/N 1043 became the only airworthy example in the world. It also holds the title of the oldest flying Boeing in the world. In 1928, the aircraft was substantially damaged in a crash and we totally rebuilt by Pemberton and Sons Aviation in Spokane, Washington.[1].